Increases in computer speeds and concurrent increases in demand for space and decreased component sizes continue to challenge the electronics industry. Recent interest and effort has grown in the area of molecular electronics as a potential solution to at least some of these problems. Only a small handful of research groups have produced molecules which act as molecular switches. Most of these molecular switches have features that limit their practical use. Initial demonstrations of molecular switches used rotaxanes or catenanes which were trapped between two electrodes. The molecular switches were switched from an ON state to an OFF state by application of a positive bias across the molecule. The ON and OFF states differed in resistance by a factor of 100 for rotaxane and a factor of 5 for catenane.
Unfortunately, rotaxanes provide an irreversible switch that can only be toggled once. Thus, it can be suitable for use in a programmable read-only memory (PROM) device; however, it is unsuitable for use in reconfigurable devices. Further, rotaxanes are complex molecules which tend to be relatively large. As a result, the switching times of these molecules can be slow. In addition, rotaxanes require an oxidation and/or reduction reaction to occur before the switch can be toggled. With respect to catenane switches, the primary concerns are the small ON-to-OFF ratio and slow switching times.
Therefore, materials and methods which allow for reversible switching and decreased switching times suitable for commercial devices continue to be sought through research and development.